That is not unusual for an animal to take up raising an animal of another species.

The one that gets to me is this pair of male flamingos, in this game park in the U.K., who have taken up living together as a gay couple. Being two males, they can't lay eggs, but the employees of the game park have started leaving an egg in the nest, and the two male flamingos take turns hatching the egg, then they take turns raising the chick to adulthood. And they have found those two male flamingos are just as good mothers/fathers as any of the female flamingos in that game park.